Challenges of Sea Navigation

Wind, War, and Weather

Determining position and maintaining direction under routine conditions depended on knowledge of winds and currents. Turbulent seas and bad weather endangered crews, threatened vessels, and spoiled the best-laid navigation plans.

Distances

Deepwater sailing called for different skills than “coasting” with landmarks in sight. On the open sea, sailors relied on dead reckoning—estimating a new position based on knowing a ship’s last position, speed, and direction. But over long distances, it was subject to ever-increasing errors.

Charts and Sailing Directions

Ignorance of vast stretches of ocean and coastline characterized navigation until well into the 19th century. Each crossing yielded information for better charts and sailing directions.

Instrument Accuracy

Finding latitude became easier with the invention of angle-finding instruments, but finding longitude remained difficult until a seaworthy clock was perfected. A heaving deck and a cloudy sky made instrument readings of Sun and stars, complicated in the best conditions, even more difficult.